Two-part foam hair dyes facilitate a dyeing operation by discharging, in foams, a mixture of a first agent containing an alkali agent and an oxidation dye and a second agent containing an oxidation agent. Compared with one-part foam hair dyes, two-part foam hair dyes can achieve a high hair dyeing effect by only one dyeing operation. Of two-part foam hair dyes, an aerosol type has such problems that it may cause uneven bleaching or uneven dyeing; a pressure container or the like made of a metal is oxidized and corroded by hydrogen peroxide; and an inner pressure of the pressure container increases excessively due to decomposition of hydrogen peroxide.
There are, on the other hand, proposed two-part hair dyes dischargeable in foams from a non-aerosol foamer container (refer to Patent Documents Nos. 1 to 6). Use of them ensures a uniform-color finish because the mixture of the first agent and the second agent can be applied uniformly to the hair. In particular, they are effective for eliminating a difference in color between a newly grown portion and an already dyed portion.
Non-aerosol two-part foam hair dyes should contain a substantial amount of a water-soluble cationic polymer in order to improve lathering and prevent dripping. On the other hand, dyes for gray hair sometimes contain a high concentration of oxidation dyes. Of oxidation dyes, those having a phenolic hydroxyl group are important oxidation dyes inevitable for providing various colors.